Fixes a few bugs in the initial handle implementation (#94)

Failure to check for invalid type on handle creation, and handle type
check was broken.

hal/lib/athena/handles/HandlesInternal.cpp

@@ -13,6 +13,7 @@
 namespace hal {
 HalHandle createHandle(int16_t index, HalHandleEnum handleType) {
   if (index < 0) return HAL_HANDLE_NEGATIVE_INDEX;
+  if (handleType <= 0 || handleType > 127) return HAL_HANDLE_INVALID_TYPE;
   // set last 8 bits, then shift to first 8 bits
   HalHandle handle = handleType;
   handle = handle << 24;